class Compiler{
    constructor(vm) {
        this.el = vm.$el
        this.vm = vm
        this.compile(this.el)
    }

    // 编译模板处理节点
    compile(el) {
        let childNodes = el.childNodes
        Array.from(childNodes).forEach(node => {
            if (this.isTextNode(node)) {
                this.compileText(node)
            } else if (this.isElementNode(node)) {
                this.compileElement(node)
            }
            if (node.childNodes && node.childNodes.length) {
                this.compile(node)
            }
        })
    }

    // 处理元素节点
    compileElement(node) {
        console.log(node);
        // 获取元素节点的属性
        Array.from(node.attributes).forEach(attr => {
            let attrName = attr.name
            if (this.isDirective(attrName)) {
                attrName = attrName.substr(2)
                let key = attr.value;
                this.update(node,key,attrName)
            }

        })
    }

    // 处理文本节点
    compileText(node) {
        let reg = /\{\{(.+?)\}\}/
        let value = node.textContent
        if (reg.test(value)) {
            let key = RegExp.$1.trim()
            node.textContent = value.replace(reg, this.vm[key])
            
            // 创建watcher对象，当数据改变时更新视图
            new Watcher(this.vm, key, (newValue) => {
                node.textContent = newValue
            })

        }
    }
    update(node,key,attrName) {
        let updateFn = this[attrName + 'Updater']
        updateFn && updateFn.call(this,node,this.vm[key],key)
    }
    textUpdater(node, value,key) {
        node.textContent = value
        new Watcher(this.vm, key, (newValue) => {
            node.textContent = newValue
        })
    }
    modelUpdater(node, value,key) {
        node.value = value
        new Watcher(this.vm, key, (newValue) => {
            node.value = newValue
        })

        // 双向绑定
        node.addEventListener('input', () => {
            this.vm[key] = node.value
        })
    }
    // 判断元素属性是否是指令
    isDirective(attrName) {
        return attrName.startsWith('v-')
    }

    // 判断节点是否是文本节点
    isTextNode(node) {
        return node.nodeType === 3
    }

    // 判断节点是否是元素节点
    isElementNode(node) {
        return node.nodeType === 1
    }
}